A patient admitted to the oncology unit develops electrolyte abnormalities including hyperkalemia, hyperphosphatemia, and hypocalcemia following initiation of chemotherapy. Which of the following conditions is most likely responsible?

1. A

   Tumor lysis syndrome

2. B

   Septic shock

3. C

   Hypercalcemia of malignancy

4. D

   Syndrome of inappropriate antidiuretic hormone (SIADH)

Appeared in: NORCET 10 Mains

Explanation

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• Tumor lysis syndrome (TLS) is a metabolic emergency caused by the massive and rapid breakdown of cancer cells, typically after the initiation of chemotherapy.
• This cell destruction releases large amounts of intracellular contents into the bloodstream.
• The key laboratory findings are hyperkalemia (from intracellular potassium), hyperphosphatemia (from intracellular phosphate), and secondary hypocalcemia (as phosphate binds with calcium).
• Hyperuricemia also occurs due to the breakdown of nucleic acids, which can lead to acute kidney injury.

Why Other Options Were Wrong

• Option B: Septic shock typically presents with hemodynamic instability, fever, and possibly lactic acidosis. While electrolyte shifts can occur, they do not follow the specific pattern of high potassium, high phosphate, and low calcium seen in TLS.
• Option C: This condition is characterized by high serum calcium levels, which is the direct opposite of the hypocalcemia presented by the patient. Hypercalcemia of malignancy is caused by bone breakdown or tumor secretion of parathyroid hormone-related protein (PTHrP).
• Option D: SIADH is a disorder of water balance, not the electrolyte pattern seen here. It leads to excessive water reabsorption by the kidneys, causing dilutional hyponatremia (low sodium).

Related Visual

• Visual 1: Flowchart - Illustrating the pathophysiology of Tumor Lysis Syndrome, starting from 'Chemotherapy-induced cell lysis' and branching to show the release of potassium, phosphate, and nucleic acids, and their subsequent effects (hyperkalemia, hyperphosphatemia, hypocalcemia, hyperuricemia) and end-organ damage (cardiac arrhythmias, renal failure).
• Visual 2: Table - A summary table of the Cairo-Bishop classification for laboratory and clinical TLS, defining the specific values for hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia.

Clinical Relevance

• Nursing practice connection: Use the key finding related to Recognition of Tumor Lysis Syndrome (TLS) based on classic electrolyte abnormalities to guide bedside assessment, documentation, and the next nursing action.
• Early recognition of TLS is critical for nurses, as it is a life-threatening emergency. Prompt intervention can prevent irreversible renal failure and fatal cardiac arrhythmias.
• Nurses are responsible for aggressive hydration, strict intake and output monitoring, and frequent assessment of lab values for at-risk patients (those with bulky, chemosensitive tumors like lymphomas and leukemias).
• What if? - If the patient's labs showed hypercalcemia instead of hypocalcemia, the primary diagnosis would shift away from TLS towards Hypercalcemia of Malignancy. The immediate nursing priority would be hydration and potentially administering bisphosphonates, not managing hyperkalemia or hyperphosphatemia.

How to Approach the Question

• First, analyze the clinical scenario: an oncology patient recently started on chemotherapy.
• Next, identify the key data provided in the stem: the specific triad of electrolyte abnormalities (hyperkalemia, hyperphosphatemia, hypocalcemia).
• Systematically evaluate each option against this classic presentation.
• Recognize that Tumor Lysis Syndrome is defined by this exact metabolic derangement following cytotoxic therapy.
• Eliminate other options by identifying their characteristic features: Septic shock (infection signs), Hypercalcemia of malignancy (high calcium), and SIADH (low sodium). This process of elimination confirms TLS as the only diagnosis that fits all the presented data.

Concept Tested & Keywords

• Concept Tested: Recognition of Tumor Lysis Syndrome (TLS) based on classic electrolyte abnormalities.
• Stem keywords: oncology unit, chemotherapy, electrolyte abnormalities, hyperkalemia, hyperphosphatemia, hypocalcemia
• Lead-in keywords: most likely responsible
• Clinical cues: The combination of hyperkalemia, hyperphosphatemia, and hypocalcemia is the classic triad for TLS.
• Clinical cues: The onset following chemotherapy is a key temporal clue.

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